The swearing-in came off without a security-related hitch yesterday, but underneath the calm veneer, federal authorities were intensively investigating a report that a group of Somalia-based militants wanted to initiate some kind of inauguration-related attack.
The day's responsibilities for most security officers ended at 4:39 p.m., when the Obamas walked under the white awning and entered the White House.
But for others it will continue, as authorities search for any indication that the Somalia-based threat was real.
Russ Knocke, chief spokesman for the Department of Homeland Security, said authorities were taking the threat very seriously but it was "of limited specificity and uncertain credibility."
One federal law enforcement official said the threat involved individuals affiliated with al Shabaab, a radical Islamist extremist group that is active in Somalia.
In recent years, U.S. authorities have become concerned that U.S.-based Somalians are traveling to Somalia to fight alongside al Shabaab and other extremists there against U.S. ally Ethiopia.